The present invention relates to a compact solid-state laser, and particularly to a compact solid-state laser used for a multiwavelength optical source for a wavelength-division-multiplexed communication system, a wide-spectrum optical source for spectroscopy, a ultra-short pulse source for distance measurement, a ultra-short pulse source for instrumentation, and the like. The invention also relates to a transmitter using this compact solid-state laser.
Various cavity structures for the solid-state laser have been proposed, as described for example in publication "Ultra Short Pulse Technology" ("KOGAKU" Japanese Journal of Optics, Vol.24, No.7, pp.378). Their basic structure includes four or more mirrors which form a cavity, a gain crystal as gain medium, and a prism pair or a grating pair which compensates the dispersion attributable to the gain crystal.
However, this basic structure has too many component parts and needs to space out the prism pair or grating pair by several tens centimeters for dispersion compensation. Therefore this structure does not allow for the compact design of a solid-state laser. In the case of pulsative operation, the repetition frequency cannot be raised unless the cavity length is made short. The conventional solid-state laser has a repetition frequency of around 100 MHz, whereas the solid-state laser used for the communication system must have a repetition frequency of several gigahertz or higher.
There is a proposal for making the solid-state laser compact so that its repetition frequency is higher, as described in the article entitled "Compact Kerr-lens model-locked resonator" by B. E. Bouuma et al. in OPTICS LETTERS, Vol.21, No.2, pp.134-136, published in 1996. The proposed compact Kerr-lens model-locked resonator has its cavity made up of three elements including a gain crystal, a curved mirror, and a prismatic output coupler.